Valorization of lignin in polymer and composite systems for advanced engineering applications – A review

Polymer/lignin blends: Interactions, properties, applications

Lignin-based thermoplastic materials have attracted increasing interest as sustainable, cost-effective, and biodegradable alternatives for petroleum-based thermoplastics. As an amorphous thermoplastic material, lignin has a relatively high glass-transition temperature and also undergoes radical-induced self-condensation at high temperatures, which limits its thermal processability. Additionally, lignin-based materials are usually brittle and exhibit poor mechanical properties. To improve the thermoplasticity and mechanical properties of technical lignin, polymers or plasticizers are usually integrated with lignin by blending or chemical modification. This Review attempts to cover the reported approaches towards the development of lignin-based thermoplastic materials on the basis of published information. Approaches reviewed include plasticization, blending with miscible polymers, and chemical modifications by esterification, etherification, polymer grafting, and copolymerization. Those lignin-based thermoplastic materials are expected to show applications as engineering plastics, polymeric foams, thermoplastic elastomers, and carbon-fiber precursors.

Lignin-Based Thermoplastic Materials

Thermal, antioxidant and swelling behaviour of transparent polyvinyl (alcohol) films in presence of hydrophobic citric acid-modified lignin nanoparticles.

In this work, PVA nanocomposite films containing cellulose nanocrystals (CNC) and different amounts of lignin nanoparticles (LNP), prepared via a facile solvent cast method, were crosslinked by adding glutaraldehyde (GD) The primary objective was to investigate the effects of crosslinker and bio-based nanofillers loading on thermal, mechanical, antioxidant and water barrier behaviour of PVA nanocomposite films for active food packaging Thermogravimetric analysis showed improved thermal stability, due to the strong interactions between LNP, CNC and PVA in the presence of GD, while Wide-angle X-ray diffraction results confirmed a negative effect on crystallinity, due to enhanced crosslinking interactions between the nanofillers and PVA matrix Meanwhile, the tensile strength of PVA-2CNC-1LNP increased from 26 for neat PVA to 354 MPa, without sacrificing the ductility, which could be explained by a sacrificial hydrogen bond reinforcing mechanism induced by spherical-like LNP UV irradiation shielding effect was detected for LNP containing PVA films, also migrating ingredients from PVA nanocomposite films induced radical scavenging activity (RSA) in the produced films in presence of LNP Furthermore, PVA-CNC-LNP films crosslinked by GD showed marked barrier ability to water vapour

https://www.mdpi.com/2073-4360/12/6/1364/pdf

Effect of Cellulose Nanocrystals and Lignin Nanoparticles on Mechanical, Antioxidant and Water Vapour Barrier Properties of Glutaraldehyde Crosslinked PVA Films.

With alkali lignin and PVA as the primary materials, glutaraldehyde as the cross-linker, and glycerin as the plasticizer, alkali lignin/PVA cross-linking reaction film was prepared by casting. The process conditions were evaluated one at a time for different variables. Mechanical properties of the composite film were tested. The performance of the reaction film was analysed by XRD, TG, SEM, and FT-IR. The results showed that when the mass ratio of alkali lignin/PVA was 1/5, glutaraldehyde content 1.67%, and glycerol content 7.1% (w/w) of the dry matter, respectively, the reaction film had satisfactory mechanical properties. Under the best conditions, the mechanical properties of the reaction film were better than that of pure PVA film. The thermal stability of the reaction film was higher than the stability of PVA film. Compared with pure PVA film, the crystallinity of the reaction film decreased a little. SEM images indicated that compatibility of alkali lignin and PVA was good. The FT-IR analysis showed that a cross-linking reaction occurred between alkali lignin and PVA(1788). But the aldol reaction between the lignin and PVA(1788) was weak.

https://ojs.cnr.ncsu.edu/index.php/BioRes/article/download/BioRes_08_3_3532_Su_Mechanical_Properties_Research/2154

Mechanical Properties Research and Structural Characterization of Alkali Lignin / Poly(vinyl alcohol) Reaction Films

On the basis of previous experiments, industrial alkaline lignin/poly (vinyl alcohol) (PVOH) cross-linked films, industrial alkaline lignin/poly (vinyl alcohol) blend films, and neat poly (vinyl alcohol) films were prepared by casting. The films were investigated by Fourier transform infra-red spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetry analysis (TGA), and dynamic mechanical analysis (DMA). The water contact angles for the three kinds of films were studied as well. The crosslinking reaction between alkaline lignin and PVOH was strong, which was attributed to the high hydrolysis degree of PVOH and the high reactivity of formaldehyde. Compared with the neat PVOH film, the crystallinity of the cross-linked film decreased slightly; the thermal stability of the cross-linked film was higher; DMA analysis showed that the Tg and the tanδ magnitude of the alkaline lignin/PVOH reaction film both decreased slightly. Lignin and the cross-linking reaction both improved the water resistance of films. Therefore, this research has provided a detailed analysis of the characterization of the films while exploring the potential of direct usage of industrial alkaline lignin in polymer materials.

https://ojs.cnr.ncsu.edu/index.php/BioRes/article/download/BioRes_09_3_4477_Su_Fang_Cross_Linked_Alkaline_Lignin/2857

Characterization of Cross-linked Alkaline Lignin/Poly (Vinyl Alcohol) Film with a Formaldehyde Cross-linker

Nickel-based magnetic activated carbon was synthesized from coconut shell activated carbon by electroless plating with palladium-free activation. The effect of plating solution volume on metallic ratio and adsorption capacity were evaluated. The effect of metallic ratio on specific area, pore volume, and magnetic properties were investigated. The morphologies of activated carbon before and after plating were observed by SEM, and the composition of the layer was analyzed by EDS analysis. The results showed that the metallic ratio was increased with the increase of the plating solution volume. The magnetic activated carbon showed high adsorption capacity for methylene blue and a high iodine number. Those values reached 142.5 mg/g and 1035 mg/g, respectively. The specific area and pore volume decreased from 943 m2/g to 859 m2/g and 0.462 ml/g to 0.417 ml/g, respectively. And the layer was more compact and continuous when the metallic ratio reached 16.37 wt.%. In the layer, there was about 97 wt.% nickel and 3 wt.% phosphorus, which indicates that the layer was a low-phosphorus one. At the same time, magnetism was enhanced, making the product suitable for some special applications.

https://bioresources.cnr.ncsu.edu/wp-content/uploads/2016/06/BioRes_06_1_0070_Jia_SHWZW_Adsorp_Prop_Ni_Mag_Act_C_Elec_Plating_1288.pdf

Adsorption properties of nickel-based magnetic activated carbon prepared by pd-free electroless plating

The invention discloses a method for preparing nickel radical magnetic active carbon, relating to a method for preparing magnetic active carbon. The invention solves the problem that the blockage of a screen and the loss of the active carbon are easily caused by using a filtering and separating method during the use of the prior powder active carbon. The method comprises the following steps of: 1, soaking the active carbon in a chitosan acetic acid solution, filtering, and then drying filtering slag; 2, activating surfaces; 3, adding the active carbon processed in the step 2 in the filtering liquid obtained in the step 2 to stir and plate, filtering, washing and drying to obtain the nickel radical magnetic active carbon. In the invention, the magnetic nickel can be introduced into the active carbon, the obtained nickel radical magnetic active carbon can be fully separated without filtering after use, thus, the invention not only solves the separation problem of the powder carbon, but also solves the problem of small adsorption capacity of the magnetic materials.

Ling Su

Papers

Mechanical Properties Research and Structural Characterization of Alkali Lignin / Poly(vinyl alcohol) Reaction Films

Characterization of Cross-linked Alkaline Lignin/Poly (Vinyl Alcohol) Film with a Formaldehyde Cross-linker

Adsorption properties of nickel-based magnetic activated carbon prepared by pd-free electroless plating

Method for preparing nickel radical magnetic active carbon by non-palladium activation method

Biomass-derived multifunctional 3D film framed by carbonized loofah toward flexible strain sensors and triboelectric nanogenerators